There is a growing use of image reproduction devices and printers, primarily laser printers, that are integrated into a computer network. Computer networks are now common in many businesses and may extend over several floors of a building facility and may have many users sharing a plurality of printers. In many installations, several of the printers that are connected to the network are located on each floor of the facility that is served by the network.
Alternatively, numerous printers connected to a computer network may be widely scattered in individual kiosks located throughout a mall type retail outlet. Such printers are typically located in the kiosks that offer a particular service and that dispense printed paper responsive to a customer's inputs at the printer site. The various printers are typically monitored at a central location located somewhere within the mall. Additionally, such kiosks may be distributed nationwide and connected through a wide area communications network to a central monitoring location, which is located at great distance from the majority of the kiosks. In this case, the paper "low" signal would prompt an operator at the central location to call the retail store where the kiosk is located to have the store personnel replenish the paper supply. In more remote locations, a kiosk service provider would be dispatched to refill the paper.
It is imperative that the printers always have a supply of paper in order to respond to the customer request. An exhausted paper supply results in the kiosk being off-line and, consequently, results in a lost sale. Typically, a person in a retail outlet that is located proximate to the kiosk is detailed to ensure that the paper supply is adequate. Preferably, such person is notified of a paper "low" condition after or before normal working hours so that replenishing the supply does not interfere with the normal activities associated with the retail outlet. It would be advantageous to decrement the number of paper sheets remaining in the cassette after initiation of a paper "low" signal so that the remaining supply could be monitored and could be replenished during normal working hours if the kiosk was experiencing an abnormally high demand and the paper supply was about to be exhausted.
Presently, printers typically have paper "out" quantity detectors only. Since the printers are closely operated, a paper "out" signal is adequate to indicate to a nearby operator that paper needs replenishing. Accordingly, most commercially available printers today have only a paper "out" detector.
With networks as have been described, a paper "out" signal indicating exhaustion of the paper supply in a particular printer is typically the only indication available that reflects the status of the paper supply. Such a signal by itself is simply not adequate for the aforementioned scenarios. A paper "low" signal, indicating that a preselected quantity of paper sheets remain in the printer, is needed so that the supply can be replenished in a timely manner and to ensure that the printer is available for use the maximum possible time. Also, decrementing the number of sheets remaining after detecting a paper "low" condition is desirable in order to trigger resupply of paper when exhaustion of the current supply is imminent.
Printers today typically draw paper from a stacked supply of paper sheets as distinct from a continuous roll of supply paper. The stacked paper sheets are loaded into a tray type cassette. In order to replenish the supply of paper sheets in such a cassette, the cassette is typically fully removed from the printer cabinet. It is important that a paper "low" detector be installed in such a manner as to not impair the ability to fully remove the cassette from the printer. Accordingly, the "low" paper detector should be located within the printer cabinet, but remote from the cassette in order to facilitate freely removing the cassette from the printer cabinet.
Additionally, it is desirable that a detector take advantage of the inherent reliability in electro optical technology as distinct from a purely mechanical detector or a mechanical/optical detector. This is especially true for the remotely located printers in the kiosks. Maintenance of such printers should a detector malfunction is not typically readily available. The paper "low" sensor should have a range of settings so that a selected quantity of paper remaining, e.g. 100 sheets or 200 sheets, may be detected as desired. Since there are a great many printers currently on the market, it is desirable that the paper "low" detector be configured to be able to be readily retrofitted into such existing printers. It is desirable that such retrofit not require physical alteration of the existing tray cassettes.
The Japanese reference 0062136 discloses a tray cassette having a paper "low" detector physically attached to the cassette. The paper "low" detector utilizes an illuminator in a vertically stacked array of optical fibers. Both the illuminator and the stacked array of optical fibers have physically attached to the cassette. Removal of the cassette from the printer cabinet is hampered by the extensive number of fiber optic and electrical connections that exist between the tray cassette and the printer cabinet.
A second paper "low" detector is presented in U.S. Pat. No. 4,928,949. The '949 patent discloses an illuminator and an optical receiver disposed below and above the stack of supply paper respectively. The paper in the particular cassette of the '949 patent is stacked at an acute angle. The detector relies on the depletion of a portion of the angularly stacked paper in order for the detector to detect the light transmission by a sensor that is positioned on an opposite side of the paper stack from the emitter and to register a paper "low" condition.